Networking Router Key points: 1. Add Conclusion at the end of Report 2. Add Abstract at the start of Report

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WHAT IS NETWORK? : The simple definition of Network can be given as under “A Network is a collection of terminals, computers, servers, and components which allows for the easy flow of data and use of resources between one another.”

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DATA COMMUNICATION: Data communications is the exchange of data between two devices via some form of transmission medium such as a wire cable, or satellite communication.

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NETWORKING: Data communications between remote parties can be achieved through a process called Networking, involving the connection of computers, media, and networking devices. A set of devises connected by communication link is called Nodes. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network. Following are the categories of Network: 1. Local Area Network (LAN): A Local Area Network (LAN) is usually privately owned and links the devices in a single office, building, or campus. Currently LAN size is limited to a few kilometers. LAN is designed to share resources between personal computes or workstations. The resources to be shared can include hardware, software, or data. LANs are distinguished from other types of network by their transmission media and topology. A LAN will use only one type of transition medium and most common topologies are bus, ring, and star. LAN has data rates in the 4 to 16 Mbps (million bits per second) range, but now days it reach 100 Mbps with gigabits systems in development. 2. Metropolitan Area Network (MAN): A Metropolitan Area Network (MAN) is designed to extend over an entire city. It may be a single network, or it may be a means of connecting a number of LANs into a larger network so that recourses may be shared LAN-to-LAN as well as device-to-device. A MAN may be wholly owned and operated by a private company, or it may be a service provided by a public company, such as a local telephone company, which is called Switched Multi-megabit Data Services (SMDS). 3. Wide Area Network (WAN): Wide Area Network (WAN) provides long-distance transmission of data, voice, image, and video information over large geographic areas that may comprise a country, a continent, or even the whole world.

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TECHNIQUE OF NETWORK COMMUNICATION: We can divide communication network in two types: 1. Circuit-switched (Connection oriented) Network: Circuit-switched networks operate by forming a dedicated connection (circuit) between two points.

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For example, telephone system. Telephone call establishes the circuit from the originating phone through the local switching office, to a remote switching office, and finally to destination telephone. Advantage: The advantage of circuit-switched network is, its guaranteed capacity of the circuit. Once a circuit is established, no other network activity will decrease the capacity of the circuit. Disadvantage: One disadvantage of circuit-switched network is its cost to establish connection. 2.

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Packet-switched (Connectionless) Network: It is generally used to connection computer. In a packet-switched network, data to be transferred across a network is divided into small pieces called packets. A packet is usually contains only a few hundred byes of data. It has identification to provide information to network hardware, how to send it to the destination. Advantage: Multiple communications among computers can be done concurrently. Disadvantage: It doesn’t provide guaranteed capacity. When network is overloaded, time required to transfer the data is increase.

SOME NETWORK DEVICE: 1. Bridge: A computer that connects two or more networks and forwards packets among them is known as Bridge. For example, an Ethernet bridge connects two physical Ethernet cables, and forwards from one cable to another exactly those packets that are not local. Bridges differs from repeaters because bridges store and forward complete packets, while repeaters forward all electrical signals. Bridges differ from routers because bridges use physical addresses, while routers use IP addresses. When bridge connects two or more Local Area Network, all those networks have same protocol. In bridging networks, computer or node addresses have no specific relationship to location. For this reason, messages are sent out to every address on the network and accepted only by the intended destination node. Bridges learn which addresses are on which network and develop a learning table so that subsequent messages can be forwarded to the right network. Bridging networks are generally always interconnected local area networks since broadcasting every message to all possible destinations would flood a larger network with unnecessary traffic. For this reason, router networks such as the Internet use a scheme that assigns addresses to nodes so that a message or packet can be forwarded only in one general direction rather than forwarded in all directions. A bridge works at the data-link (physical network) level of a network, copying a data frame from one network to the next network along the communications path. A bridge is sometimes combined with a router in a product called a brouter. 2.

Ethernet: It is LAN technology invented at the Xerox Corporation Palo Alto research center. An Ethernet itself is a passive coaxial cable.

3.

Host: Any end-user computer system that connects to a network. Hosts may be personal computer to supercomputer.

4.

Hub: An electronic device to which multiple computers attach, using twisted pair wiring. Hub technology is popular for Ethernets.

5.

Repeater: A hardware device that extends a LAN. A repeater copies electrical signals from one physical network to another. It is not much more popular.

6.

Switch: Switch is generally used for the connecting more number of computers. It is generally used to connect two networks, which is connected by Hub.

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Gateway: It is a network point that acts as an entrance point to another network.

INTERNET ARCHITECTURE: We know that machines are connected to each other and make Network. Now the question is that how networks are interconnected to each other and make Internetwork? Physically two networks can only be connected by a computer that attaches to both of them. This computer passes packets from one network to another network. Computer that interconnects two networks and pass packets from one to another is called internet gateways or internet routers. Consider the following example shown in Fig. 1. There are two networks “Network-1” and “Network-2”. Both networks are connected by router “R”. Here network is either LAN or WAN. Router “R” passes the packet from “Network-1” to “Network-2” as well as from “Network-2” to “Network-1”.

R

Network-1

Netowork-2

Fig. 1 Two Network Connection

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ROUTER – AN INTRODUCTION: A router is the device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP’s network. Routers are located at gateways, the places where two or more networks connect. When internet becomes too complex, routers need to know the topology of entire internet network rather than particular network. Consider the following example, in which, there are three networks are connected by two routers. In this example router “R1” transfers all packets from “Network-1” to “Network-2” and vice-a-versa. Similarly router “R2” transfers all packets from “Network-2” to “Network-3” and vice-a-versa. Now when packets from “Network-1” to “Network-3”, first packet is passed to “Network-2” by router “R1” and then passed to “Network-3” by router “R2”. So for a large internet having more networks routing decision becomes more complex.

Network-1

R1

Network-2

R2

Network-3

Fig. 2 Three Network Connection Principle of Router: Router is generally small computer, having little or no disk storage and limited main memory. Router doesn’t store information about every machine or host in internet, that how to send the packet to that. But router stores information about number of networks in internet. Main principle about router is: “Router uses the destination network, not the destination host, when routing a packet.”

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IP ADDRESS: -

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To make our communication system universal, it needs a globally accepted method to identifying each computer that attaches to it. To identify each host uniquely it has given unique name, address, or route. In Internet each host has assigned 32-bit integer address called its internet address or IP address. This number is divided into four parts. Each part contains 8-bits. Generally IP address is represented in decimal value in four groups. Each group is separated by dot (.). For example, consider the following IP address of 32-bit number. It is divided into group of 8-bits as shown under. In decimal format this IP address is represented as 182.42.21.194 Binary IP address Decimal Representation

10110110 182

00101010 42

00010101 21

11000010 194

IP address doesn’t identify each host uniquely but it identifies each network connection uniquely. For example, consider one host is connected with two different networks then it should have two different identifications. Such type of host is known as multi-homed host. So the principle of IP address is: “IP address is 32-bit number which identifies each network connection uniquely but not each host.” Due to above principle, IP address has one drawback that is if any host moves from one network to another network its IP address will change. This IP address should be defined uniquely so there should be any authority that assigns these IP addresses. INTERNIC (INTERnet Network Information Center) has given this authority and it assigns IP address.

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IP ADDRESS CLASS: Conceptually, IP address is divided into two parts: One part identifies the network known as netid and another part identifies host under network known as hostid. Based on these two parts we can categories IP address into five different classes. 1. Class-A: Out of 32-bits, class-A has first bit always 0 that means 0th bit is always zero (Here bit number is from 0 to 31). Then 7-bits are used to identify network that means bit number 1 to 7 are used as netid. Remaining 24-bits (bit number 8 to 31) are used as hostid. 2. Class-B: It has first 2-bits are 10 (0th bit is 1 and 1st bit is 0). Then 14-bits (2nd bit to 15th bit) are used as netid. Remaining 16-bits (16th bit to 31st bit) are used as hostid. 3. Class-C: It has first 3-bits are 110 (0th bit and 1st bit are 11 and 2nd bit is 0). Then 21-bits (3rd bit to 23rd bit) are used as netid. Remaining 8-bits (24th bit to 31st bit) are used as hostid. 4. Class-D: It is special class used for multicast addressing. It has first 4-bits are 1110 (0th bit, 1st bit, and 2nd bit are 1 and 3rd bit is 0). Remaining 28-bits (4th bit to 31st bit) are used for multicast address. 5. Class-E: It is also special class reserved for future use. It has first 5-bits are 11110 (0th bit, 1st bit, 2nd bit, and 3rd bit are 1 and 4th bit is 0).

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DIRECT AND INDIRECT DELIVERY: In direct delivery, transmission of a datagram from one machine to another via single network. This means source machine and destination machine are connected directly via single network.

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Unlike direct delivery, there is no direct connection via single network between source network and destination network.

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TABLE-DRIVEN IP ROUTING: Generally, for routing, Router uses Internet routing table or IP-Routing table. Both host and router route data gram (packet) both have IP-routing table. This routing table stores the different network prefix of IP-address. Routing table stores (address) information whether the packet is directly deliverable or not. If not then sends it next router using that router address. Consider the example of routing having the four networks and three routers. The networks have the netid 10.0.0.0, 20.0.0.0, 30.0.0.0, 40.0.0.0 and three routers are P, Q, and R. First host is connected with the network 20.0.0.0 using router P and so on. When host has to send the packet it sense to router P, Q or R as shown in the following Fig.1 and Fig.2 shows the IP-routing table.

20.0.0.2

Network 10.0.0.0

Q

30.0.0.9

Network 20.0.0.0 20.0.0.7

10.0.0.5

Network 30.0.0.0

P

30.0.0.5 R

40.0.0.14 Network 40.0.0.0

To Reach host on network (netid) 20.0.0.0 30.0.0.0 10.0.0.0 40.0.0.0

Routing address Direct Deliver Direct Deliver 20.0.0.0 30.0.0.0

Fig. 2 Routing Table Of Router Q Hear router Q can send directly data gram to network 20 and 30. So, if there is any data gram for any host of network 20 or 30 then it can directly send data gram to that host but if any data gram for network 10 then it first search the routing table and find out the next router IP-address which connected to the network 10 from the table and same case is possible for network 40.

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DEFAULT ROUTE: Whenever there are multiple networks then all this network information is stored in to IP- routing table of each router so this routing table becomes large. So, to avoid all this information or minimize this information default route is used. Default routes are useful for small sets of

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networks. Routing table contain the information about the directly connected networks and for other networks, which are not directly connected, send the data gram to the default route. For the large set of the networks first router checks routing table and if there is a address of the network (destination) is found which is either directly connected to that address. If address is not found in routing table then send packet to the default route. Now, in general we can define the routing algorithm based on IP-routing table and default route as under: Start Read IP-address of destination data gram D. Determine networks prefix (netid) N. If Router netid = netid N. then Send data gram directly. Else if find the netid in routing table If address is found then Send data gram to next Router address from table. Else Send to the default route. End if. End if. End.

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INTERNET CONTROL MESSAGE PROTOCOL (ICMP): To allow router in Internet to report error or provide information about unaccepted circumstances the designer address Internet control massage protocol (ICMP). It reports any error to the source host.

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CONGESTION: IP is connectionless there for router can overrun with the traffic and that condition is known as congestion. There are two reasons for congestion 1. A high-speed computer is generates traffic faster then the network can transfer it. 2. Many computers simultaneously send data to the single router. When data gram arrive too fast to the router, router store then in to memory temporarily. But if memory is full then arriving data grams are discarded and source_host has send ICMP massage.

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ROUTING IN INTERNET: Routing is the technique by which data finds its way from one host computer to another. In the Internet context there are three major aspects of routing 1. Physical Address Determination: The first of these is necessary when an IP datagram is to be transmitted from a computer. It is necessary to encapsulate the IP datagram within whatever frame format is in use on the local network or networks to which the computer is attached. This encapsulation clearly requires the inclusion of a local network address or physical address within the frame. 2. Selection of inter-network gateways: The second of these is necessary because the Internet consists of a number of local networks interconnected by one or more gateways. Such gateways, generally known as routers, sometimes have physical connections or ports onto many networks. The determination of the appropriate gateway and port for a particular IP datagram is called Routing and also involves gateways interchanging information in standard ways. 3. Symbolic Addresses: The third aspect, which involves address translation from a reasonably human friendly form to numeric IP addresses, is performed by a system known as the Domain Name Service (DNS) for short. It is not considered further at this stage.

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SAMPLE ROUTER DEVICE: Following are the various types of router devices available from various manufacturers. 1. In Fig. 1 we have shown the router with 4-port pin and it has also printer port.

Fig. 4 Router with 4-Pin Port 2.

In Fig. 2 we have shown the router with 8-port pin and it has also printer port.

Fig. 5 Router with 8-Pin Port

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OPTOELECTRONIC TELECOMMUNICATION ROUTER: Optoelectronics communication provides high bandwidth. At present, single wavelength bit rate for optical fibers are between 2-6 Gbits/Sec. By Wave Division Multiplexing (WDM) and Time Division Multiplexing (TDM) it can reach upto 1 Tbis/Sec (1000 Gbits/Sec). Ultrafast routers are worked based on this principle.

Optical Wave

OET (Optical-toElectrical Transducer)

Digital Processing Network (Routing Circuit)

EOT (Electricalto-Optical Transducer)

Optical Wave

Fig. 6 Principle of Optoelectronics Router Here information arrives in forms of optical pulse or wave to the router input port. These optical pulses are converted into electrical pulses using OET. Next information packets are routed to the appropriate output address using ultrafast electronics processing network. Finally the signal is again converted to optical form using EOT. Here routing circuit is based on SFQ (Single Flux Quantum) circuits, which provides high speed and design simplicity.

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SAFETY GUIDELINES DURING INSTALLING ROUTER: Observe the following guidelines to ensure your safety and protect the equipment. This list does not identify all of the potentially hazardous situations that you may encounter in the workplace, so be alert and exercise care when working with any of the switch router’s electrical or electronic components.  Always disconnect all power cords and line card interface cables before moving the Cisco 12008.  Keep tools and switch router components away from walkway areas.  Do not work alone if potentially hazardous conditions exist in the work area.  Do not take any action that poses a potential hazard to yourself, other personnel, or the equipment.  Carefully examine your work area for potential hazards, such as damp floors, ungrounded power extension cables, and missing safety grounds.  Before beginning any procedure requiring access to the card cages or other interior switch router components, locate the emergency power-off switch for the room in which you will be working.  Never assume that power has been disconnected from a circuit; always verify that power has been removed before working on the switch router.

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 Never install telephone jacks in wet or damp locations unless the jack is specifically designed for use in such areas.  Never touch un-insulated telephone wires or terminals unless telephone lines are disconnected at the network interface.  Use caution when installing or modifying telephone lines.  Always use an ESD-preventive (Electrostatic Discharge) wrist strap and ensure that the strap makes adequate contact with your skin.

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AN EXAMPLE-ACCESS SDLC ROUTER: The Access SDSL Router is designed to offer cost-effective, high-speed services to remote offices, large enterprise and service providers, by supporting the same bandwidth for upstream as downstream over a single wire pair. The Access SDSL delivers configurable line rates up to 2.3 Mbps comparable to an T1/E1 connection. The Access SDSL Router provides a 10/100BaseTx interface, two E1/T1 serial interfaces and 24 SDSL port for connection to a SDSL link. Optional support for splitter equipment enables users to enjoy voice calls and Internet access on the same phone line without changes.

Fig. 7 Access SDLC Router Network

Fig. 8 Front Panel of Access SDLC Router

Fig. 9 Back Panel of Access SDLC Router Following is the hardware specification of Access SDSL Router. Mithil

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Features CPU Flash Memory SDRAM Memory SDLC Ports WAN Port Ethernet Port Console Port Input Voltage (AC) Output Voltage, DC The Maximum Power Supply Power Consumption Frequency Operating Temperature Storage Temperature Operating Humidity

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Access SDLC Router MPC 8240-200 MHz 4 MB, Expandable to 32 MB 64 MB, Expandable to 128 MB 24 SDLC Ports, RJ-11 connectors 2 E1/T1 Ports, DB-25 connector One 10/100 Base Tx Ethernet Port One console port, RJ-45 connector 90 to 130/170 to 260 V, auto-ranging 5V, 20A 100W 72W 50/60 Hz 32° to 140° F (0° to 60° C) -40° to 176° F (-40° to 80° C) 0% to 90% (non-condensing)

AR SERIES ROUTER SOFTWARE VERSION 2.0.2-A SOFTWARE USED FOR ROUTER: The Allied Telesyn International announces the release of Software Release 2.0.2 for the AR series of multiprotocol routers. Following are new features included into version 2.0.2: 1. Support for a new router model, the AT-AR740 2. Support for redundant power supplies and power supply monitoring 3. Configurable links speeds on 10/100 Mbps Ethernet interfaces 4. A new hunt group feature and enhanced logging for X.25 5. New MODULE trigger type 6. Improved attack notifications and triggers in the Nemesis firewall 7. Implementation of OSI Connectionless Network Service (CLNS), End System to End System routing (ESIS), and End System to Intermediate System routing (ISIS) protocols 8. Implementation of the Virtual Router Redundancy Protocol (VRRP) for fault tolerant internet gateways Software Release 2.0.2 adds significant enhancements to X.25 call handling, management, and usability including: 1. Enhanced mechanisms for terminating X.25 calls to DTEs with the addition of hunt groups. 2. A new SHOW X25C PATH command to monitor X25C calls. 3. New log messages to record interface and call transitions. 4. New triggers for handling X.25 events.

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Fig. 11 X.25 DCE hunt group

A hunt group is a set of DCE-to-DTE links that can be accessed from a remote calling DTE via a single DTE address. The DCEs in the hunt group work together to find a free LCN in the hunt group that the remote calling DTE can use to connect to a local DTE. A hunt group consists of up to 10 DCEs, and up to 6 X.25 lines per DCE. Each DCE can be a member of up to 6 hunt groups. All the DCEs in a hunt group must be on the same LAN. Any one X.25 line on a DCE can only be in one hunt group. A hunt group is accessed by a remote DTE via the hunt group DTE address which must not the same as the DTE address of any of the X.25 lines in the hunt group. Figure 11 on page 14 shows a typical scenario. DTE 1 wants to access a service that is provided either by a DTE that has multiple DTE addresses (e.g. DTE 3), or multiple DTEs sharing the load (e.g. DTEs 2, 3 and 4). In a standard X.25 network, DTE 1 sends a call request to the network with the DTE address of the DTE being called (e.g. B3 for DTE 3). If there are no free logical channels on the X.25 line with the specified DTE address (B3) then the call is cleared. DTE 1 effectively receives a busy signal. Virtual Router Redundancy Protocol (VRRP): Software Release 2.0.2 implements the Virtual Router Redundancy Protocol (VRRP), as defined in RFC 2338. One of the most common functions performed by routers is to act as the gateway to the WAN for hosts on the local LAN. On larger LANs, two or more routers may act as the gateway, and a dynamic routing protocol such RIP or OSPF is used by the hosts to determine which gateway router to use as the next hop in order to reach a particular IP destination. However, there are a number of factors, such as administrative or processing overhead, which make it undesirable to use a dynamic routing protocol. One alternative is to use static routing, but if the statically configured first hop router fails, the hosts on the LAN will be unable to communicate with hosts on the WAN. VRRP provides a solution to the problem by combining two or more physical routers into a logical grouping called a virtual router (VR). The physical routers in the virtual router operate together to provide a single logical gateway for hosts on the LAN. The virtual router has a unique identifier, called the virtual router identifier (VRID), and a virtual MAC address. The VRID is a user-defined value in the range 1 to 255. The MAC address is derived from the VRID, and is known to all the routers in the virtual router. All hosts on the LAN are configured with an IP address to use as the first hop. Typically this IP address is owned by the preferred router in the VR. When available, the preferred router acts as the master router for the VR. The master router performs the gateway functions of the virtual router, including:

   

Responding to ARP requests for the IP address(es) associated with the VR by supplying the virtual MAC address of the VR so that the hosts on the LAN will associate the virtual MAC address with their configured first hop IP address. Forwarding packets with a destination link layer MAC address equal to the virtual MAC address. Accepting packets addressed to the IP address(es) associated with the VR, if it actually owns the address(es). Broadcasting advertisement packets at regular intervals to the other routers in the VR to inform them that it is still acting as the master router.

The other routers in the VR are referred to as backup routers. The primary role of backup routers is to listen for advertisement packets from the master router. If an advertisement packet is not received for a given period, the backup routers participate in an election to elect a new master router that will take over the duties of the VR. The election is won by the router with the highest priority amongst the available backup routers. The priority is a value in the range 1 to 255. The value 255 is reserved for the router that actually owns the IP address associated with the VR. The new master router takes over all the functions of the original master router. Hosts on the LAN can continue sending packets to the same virtual MAC address, which they associate with the configured, first hop IP address, even though the router that owns the IP address is not currently available. Mithil

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Open System Interconnection (OSI): Software Release 2.0.2 adds support for the Open System Interconnection (OSI) network layer protocols:  Connectionless Mode Network Service (CLNS)  End System to Intermediate System routing exchange protocol (ESIS)  Intermediate System to Intermediate System routing exchange protocol (ISIS) All mandatory parts of the Connectionless Mode Network Service (CLNS) as defined in the following standards:  ISO 8473-1, “CLNS Protocol Specification” defines the protocol used between Network entities in end systems, between Network entities in intermediate systems, or between a Network entitiy in an end system and a Network entity in an intermediate system. In an end system, it provides the connectionless-mode Network service defined in CCITT Rec. X.213 (ISO/IEC 8248).  ISO 8473-2, “CLNS over ISO 8802 Subnetworks” specifies the way in which the underlying service assumed by the protocol defined by ISO/IEC 8473-1 is provided by a subnetwork that conforms to ISO/IEC 8802 through the operation of a subnetwork dependent convergence function (SNDCF) as described in ISO/IEC 8648. The SNDCF specified by this International Standard may be used with any ISO/IEC 8802 compliant subnetwork that provides the logical link control sublayer interface service defined by ISO/IEC 8802-2.  ISO 8348, “Network Service Definition” defines the service provided by the Nework Layer to the Transport Layer at the boundary between the Network and Transport Layers of the Reference Model. It provides for the designers of the Transport protocols a definition of the Network Service existing to support the Transport protocol and for the designers of Network protocols a definition of the services to be made available through the action of the Network protocol over the underlying service.  ISO 8343/Addendum 2, “Network layer (NSAP) addressing using preferredbinary encoding” defines the OSI Network Service.  ISO 8648, “Internal organisation of network layer” defines the internal organisation of the network layer.  ISO TR 9575, “OSI Routing Framework” describes the framework, concepts and terminology used in OSI routing protocols.  ISO TR 9577, “Protocol identification in the network layer” describes how to discriminate between multiple network-layer protocols running on the same medium. The following optional parts of CLNS:  Lifetime control determines whether a received PDU may be forwarded or whether its assigned lifetime has expired, in which case it shall be discarded.  Segmentation is performed when the length of a protocol data unit is greater than the maximum service data unit size supported by the underlying service to be used to transmit the PDU.  Reassembly reconstructs the Initial PDU from the Derived PDUs generated by the operation of the segmentation function on the Initial PDU (and, recursively, on subsequent Derived PDUs).  Error reporting attempts to return an Error Report PDU to the source Network entity when a protocol data unit originated by that Network entity is discarded.  Echo request and Echo response is invoked by Network layer management to obtain information about the dynamic state of the Network layer with respect to the reachability of specific Network entities and the characteristics of the path or paths that can be created between Network entities through the operation of Network layer routing functions.  Route recording records the path taken by a PDU as it traverses a series of intermediate systems.  Quality of Service provides information to Network entities in intermediate systems which may be used to make routeing decisions where such decisions affect the overall QoS provided to NS users.  Congestion notification informs the destination Network entity of congestion through the use of a flag in the QoS maintenance parameter in the options part of the PDU header, to Mithil

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allow NS users to take appropriate action when congestion is experienced within the NSprovider.

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AN EXAMPLE-AT-AR740 ROUTER: The AT-AR740 router extends the AR700 series of modular network access routers with a costeffective, multi-service platform for larger branch office and corporate locations demanding high data throughput, upgradeable connectivity and support for multiple WAN services

Fig. 10 Front Panel of AT-AR740 Router

Fig. 11 Rear Panel of AT-AR740 Router Main features of this router are as under: 1. High performance RISC-based architecture 2. 1 MByte of EPROM 3. 16 MBytes SDRAM 4. 6 MBytes of FLASH memory 5. 2 x 10/100 Mbps autosensing Ethernet LAN ports 6. 2 x RS-232 asynchronous serial ports 7. 2 x PIC (Port Interface Card) slide-in bays 8. 1 x NSM (Network Service Module) bay 9. A MAC (Mini-Accelerator Card) compression/encryption card slot 10. zA PAC slot 11. Redundant power supply (RPS) and -48V DC power supply options 12. Support for the full AR router software suite As shown in Fig. 10, router has two PICs (Port Interface Cards). They can accommodate any combination of following side in interface cards: 1. AR020 PRI E1/T1 PIC, 1 Primary Rate E1/T1 port 2. AR021(S) BRI-S/T PIC, 1 Basic Rate ISDN S/T port 3. AR021(U) BRI-U PIC, 1 Basic Rate ISDN U port 4. AR022 ETH PIC, 1 Ethernet LAN AUI/10BASET port 5. AR023 SYN PIC, 1 Synchronous port with universal 50-way AMPLIMITE connector 6. AR024 ASYN4 PIC, 4 Asynchronous ports with RJ45 connectors 7. AR025 PRI E1 PIC, 1 Primary Rate/G.703 E1 port Mithil - 12 -

As shown in Fig. 10 router has 4-PIC NSM (Network Service Modules). It is designed to support high-speed LAN/WAN technologies. The NSM uses a 32MHz 32-bit PCI style bus for high-speed data applications. The first NSM to be released is the AT-AR040 4-PIC NSM, which has 4 PIC bays for installing PICs. The NSM will also be supported on Allied Telesyn’s new range of Layer 3-gigabit switches, providing WAN connectivity of high speed switching applications. Router has Mini-Accelerator Cards (MACs). The dedicated MAC (Mini Accelerator Card) slot can accommodate any of the following MAC cards: 1. AT-AR010 EMAC, Encryption MAC card. 2. AT-AR011 ECMAC, Compression/Encryption MAC card. 3. AT-AR012 CMAC, Compression MAC card The AT-AR740 has a DB25 connector for connection to a redundant power supply (RPS) unit, such as the AT-AR740RPS. AR Router Software Release 2.0.2 includes new monitoring functions for the PSU and fan in both the AT-AR740 and the RPS. The AT-AR740 is also available in a 48V DC factory fit option designed for installation at telecommunication carrier sites.

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ROUTER CIRCUIT: In Router circuit design first we design a simple solid-state circuit and later on we design 2 – input, 2 – output router circuitry. In simple solid-state circuit there is one input and one selector line. There are two output signals. Incoming signal comes via input line. Selector line is selected in such a way so there is output is either goes to Output–A or Output–B. Here we are using one NOT gate and two AND gates.

Input

Output A

Output B

Selector Fig. 3 Simple State Router Circuit

Now we design 2–Input, 2–Output Router circuit. It is simply known as 2x2 router circuit. This Router circuit contains following components:

 D-type, positive edge-triggered with synchronous clear, flip-flop.  4-Input, 2-Oupput Multiplexer.  2-Input, 1-Output asynchronous Multiplexer. We have divided entire circuit in multiple sections. All sections connected to each other make whole circuit. There are following sections: 1. Generate SCLR output: Mithil

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Reset

SClr

Here we are using NOT gate to generate SClr signal from Reset signal. 2. First Level of Input delay using D-Flip Flop series: This section has two D-Flip Flops, which has Input-0 and Input-1 as input line respectively. Also it has Clock signal and SCLR input from SClr signal from section-1. This section delay input signal by one clock cycle to read both header bit of two input signal at same time. D Flip-Flop 1 Input-0

D

Clock

CLOCK

SClr

A

Q

SCLR D Flip-Flop 2 D

Input-1 Clock

CLOCK

B

Q

SCLR

SClr

3. Second Level of Input delay using D-Flip Flop series: This section has also two D-Flip Flops, which has output of section-2 as input. Also it has SClr and Clock as input line. This second level of circuit is also used to delay signal by one clock cycle, which routes the signal to appropriate destination.

D Flip-Flop 3 A Clock SClr

D CLOCK

C

Q

SCLR D Flip-Flop 4

B Clock SClr

D CLOCK

D

Q

SCLR

4. 4x2 Multiplexer: This section contains simple 4-Input, 2-Outpu Multiplexer. Out of its four inputs two inputs come from direct input signals Input-0 and Input-1. Remaining two inputs come from section-2 outpus as A and B. It has also Clock signal, Reset signal, and Adder Bit as input. 4x2 Multiplexer

Mithil

Input-0

IN0A

A

IN0B

Input-1

IN1A

B

IN1B

Clock Addr

CLOCK ADDR BIT

CLASH

MUXSELECT

E- 14 -

F

5. 2x2 Multiplexer series: This section contains two 2x2 multiplexers. Here total six inputs are there. Output of these six inputs two inputs are coming from section-3 as C and D. One input is coming from the section4 as F (MUXSELECT output of Multiplexer) 2x1 Multiplexer IN0 G

IN1 RESULT

SEL C 2x1 Multiplexer IN0

D

H

IN1 RESULT

SEL

F

6. Final Output using three D-Flip Flop: This section has three D-Flip Flops. It has input from section-5 as G and H. Also it has CLASH output of section-4 as E. Also there is present of clock signal and SClr signal. There is OR operation of E output and SClr signal is made using OR gate and input as SCLR signal. D Flip-Flop 5 G

D CLOCK

Q

Output-0

SCLR D Flip-Flop 6 H Clock

D CLOCK

Q

Output-1

SCLR D Flip-Flop 7 E

D CLOCK

SClr Mithil

Q

Clash

SCLR - 15 -

Principal of above Circuit: The section-1 clock cycle delay until the whole two-bit header becomes readable. Once the header is available, the routing decisions are made in the next state. There, the outputs of this machine to be used in the router2x2 circuit are decided. The ‘MuxSelect’ output signal is set to zero if ‘Input0’ has to be routed to ‘Output-0’, and ‘Input-1’ has to be routed to ‘Output-1’. Otherwise, it is set to one. The decision concerning this action is based on the ‘Addr_bit’ signal, which determines which header bit should be used to determine the destinations of the packets.

Mithil

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